Audio beam-forming and sound source localization techniques are widely deployed in conjunction with applications such as teleconferencing and speech recognition. Beam-forming and sound source localization typically use microphone arrays having multiple omni-directional microphones. For optimum performance, the microphones of an array and their associated pre-amplification circuits should be precisely matched to each other. In practice, however, manufacturing tolerances allow relatively wide variations in microphone sensitivities. In addition, responses of microphone and pre-amplifier components vary with external factors such as temperature, atmospheric pressure, power supply variations, etc. The resulting mismatches between microphones of a microphone array can greatly degrade the performance of beam-forming, sound source localization, and other sound processing techniques that rely on input from multiple microphones.